Update express-mode-weather-agent.ipynb

[uedayo]

Add missing code section for # Create Vertex AI Memory through ADK to use locally

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[koverholt]

Cross reference: follow up to #883.

[koverholt]

@uedayo, the CLA check is failing per https://github.com/google/adk-docs/pull/941/checks?check_run_id=55080805576. Could you sign the CLA (or register your GitHub account at go/github if you are a Googler).